Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$204.29	12.460%	$229.7445	$229.74	$229.75	$229.70
Purchase #2	$16.30	11.369%	$18.1531	$18.15	$18.15	$18.20
Purchase #3	$136.50	3.865%	$141.7757	$141.78	$141.80	$141.80
Purchase #4	$215.27	10.768%	$238.4503	$238.45	$238.45	$238.50
Purchase #5	$212.50	9.448%	$232.577	$232.58	$232.60	$232.60
Purchase #6	$75.26	13.590%	$85.4878	$85.49	$85.50	$85.50
Purchase #7	$98.38	13.192%	$111.3583	$111.36	$111.35	$111.40
7 purchase totals =	$958.50		$1,057.5467	$1,057.55	$1,057.60	$1,057.70